This invention relates to the field of measurement while drilling (MWD) and borehole telemetry. More particularly, this invention relates to a method and apparatus for wireless or remote communication of control or data information from the equipment operator to the MWD system.
In the field of borehole drilling, particularly oil and gas well drilling, the usefulness of systems capable of detecting parameters at the bottom of the drill string and transmitting such data to the surface during the course of drilling has long been recognized. Mud pulse telemetry systems are known and in commercial use for measuring while drilling. Such systems are shown, for example, in U.S. Pat. Nos. 3,982,431; 4,013,945 and 4,021,774 all of which are assigned to the assignee hereof.
An MWD system is comprised of various borehole sensors combined with a computer controlled data acquisition system and a mud pulse telemetry system. In use, an MWD system is exposed to extremes of mechanical stress due to shock and vibration, hydrostatic pressure of the mud, and temperature. These extremes require that the electronics be contained in a package of high integrity. Further, this package is placed inside a drill collar making access difficult.
Changing drilling conditions often make it desirable to be able to affect changes in the operating parameters of the MWD system at the rig site. It is commonly understood that by interconnecting two computers at the surface using an interface as described in EIA Standard RS232, a hard wired communications link can be established. Once established, data, control or programs can be transferred between the computers.
Unfortunately, the use of a RS232 communications link suffers from certain problems. For example, electrical connectors must be provided to the effect the RS232 link. In the MWD tool, this connector is associated with an opening through the drill collar. It will be appreciated that adding the necessary features (such as the opening through the drill collar) for effecting direct electrical connection to the MWD tool can add considerable cost to the MWD system as well as increase the risk of system failure in downhole use.